Centrifugal separator



Dec. 26, 1961 K. J. R. LUNDBERG I 3,014,642

CENTRIFUGAL SEPARATOR Filed March 26, 1958 ATT R Y limited rates 3,014,642 CENTRIFUGAL EPARATR Karl Johan Reinhold Lundberg, Mariehall, Sweden, assignor to Aktieholaget Separator, Stockholm, Sweden Filed Mar. 26, 1958, Ser. No. 724,183 Claims priority, application Sweden Apr. 3, 1957 4 Claims. (Cl. 233-22) This invention relates to centrifugal separators of the type in which a separated material, discharged through nozzle outlets in a peripheral zone of the centrifugal rotor, is collected in an annularreceptacle surrounding the rotor and located in the separator frame, the recep tacle having an annular slot opening toward the nozzles and having an outlet for the collected material. More particularly, the receptacle is provided with an annular inner wall extending axially of the rotor and terminating near it at a region located radially inside the nozzle outlets and at one side of the nozzle zone, and with an annular outer wall extending opposite the nozzle outlets and radially inward toward the centrifugal rotor, with which it forms a free annular space at the opposite side of the nozzle zone.

Centrifugal separators of this kind are subject to the inconvenience that the outer surfaces of the receptacle and of the centrifugal rotor or bowl, as well as the inner surfaces of the frame, are dirtied by the material which is thrown out through the nozzles and which in most cases contains sludge. If the sludge consists of yeast or resinous substances, the cleaning is both troublesome and costly.

The causes of the dirtying are numerous. The receptacle, because of its shape, cannot to advantage be made in one piece but is usually made in two pieces, which are then welded together. Consequently, it is both costly and troublesome to make the edges of the annular slot so exact that these edges, after the receptacle has been fitted into a locating recess in the frame, will fit closely and accurately to the centrifugal rotor at opposite sides of the nozzle zone. Any fine-trimming of the receptacle edges after the welding would involve a rather expensive operation.

In addition, the rotation axis of the centrifuge is variable and, during running of the centrifuge, may assume a position at variance with the edge of the receptacle which was previously trimmed to lie as close as possible to the mantle surface of the centrifugal rotor. Consequently, it has been necessary to make the spacing or slot between the receptacle and the rotor mantle surface greater than desired. This, in turn, has meant that some of the material spouting from the rotor nozzles will splash out through the slot and dirty the outer surfaces of the receptacle and of the centrifugal rotor as well as the inner surfaces of the frame. The splashing of the material through the slot is increased by the sucking fanaction which the rotating centrifugal bowl exerts upon air and material in the receptacle. Finally, the abovementioned surfaces are dirtied because the material, in passing from the receptacle outlet through a discharge line secured in the frame, splashes or is sucked in between the receptacle outlet spout and the discharge line. For practical reasons, the receptacle spout is not secured to the discharge line, as the receptacle should be readily removable for internal or external cleaning.

The principal object of the present invention is to provide a centrifuge construction which overcomes the above-noted difficulties.

In a centrifuge made according to the invention, an annular and substantially fiat screen rests against the radially inwardly directed part of the outer annular wall of the receptacle, this screen having its outer edge centered by a surrounding part of the frame. At its inner edge, the screen has an annular flange which extends into the receptacle and is in closely surrounding but spaced relation to the centrifugal rotor, this flange overlapping the free edge of the radially inwardly directed part of the outer wall of the receptacle. A cover of the frame presses the screen against the receptacle, and thereby holds the latter against its locating seat on the frame. On its side which is remote from the receptacle, the screen is preferably provided with vanes and with springs which transmit the pressure of the cover to the screen. A packing is preferably secured between the spout of the receptacle and the discharge line of the frame.

The new centrifuge has the advantage that the receptacle can be made in a simple and cheap way from two parts, a lower and an upper half, which are welded together. The opening of the receptacle slot may be made relatively wide so that the receptacle interior is readily accessible for cleaning. This is possible because the radially inwardly directed outer wall of the receptacle need not extend as far radially inward toward the rotor as heretofore, since the screen, centered by the frame, rests against the receptacle and extends close to the centrifugal rotor so as to form a slight slot with it. The inner annular wall of the receptacle should, on the other hand, fit closely to the centrifugal rotor, but this presents no diificulty even though the rotor axis during operation takes different positions in the frame, because there is only a very slight change in the axial position of the rotor. It is, of course, much simpler and cheaper to adjust the screen to provide a small slot around the rotor than to adjust the edge of the receptacle for this purpose. The vanes on the screen have the advantage that when the rotor works as a pump and entrains air, this air is caught by the vanes which dam up the air at the slot and thereby counteract sucking action through the slot. Finally, the packing in the space between the spout and the discharge line prevents sludge from passing through this space either by splashing or by sucking action.

A preferred embodiment of the invention is described more in detail below, reference being made to the accompanying drawing in which:

FIG. 1 is a vertical sectional view of part of a centrifuge embodying the invention, the rotor being shown in elevation, and

FIG. 2 is a plan view of part of the screen, showing some of the vanes and one of the springs.

Referring to the drawing, the separator there shown comprises a hollow rotor body of centrifugal bowl 1 having an axial spindle 2 mounted for rotation in a frame 3, the spindle being driven by a suitable motor (not shown). The rotor 1 has peripheral nozzles 4 which, during operation, spout a liquid (generally mixed with sludge) at a high velocity into an annular stationary receptacle 5 which surrounds the rotor and is provided with a discharge spout 6. The receptacle has a bottom '7, an annular inner wall 8, and an annular outer wall 9. The inner wall 8 extends axially (upward) toward the rotor body 1 and terminates at its upper edge in the immediate vicinity of the rotor and at a distance radially inward from the nozzles 4. The outer wall 9 extends first a distance axially upward past the nozzles and then a distance radially inward toward the rotor body above the nozzles 4. The inner annular wall 8 and the radially inwardly directed part of the wall 9 form between their terminal edges an annular open slot 10, into which the rotor body with its nozzles 4 extends at least partly in order to enable the receptacle 5 to catch the jets of mate rial from the nozzles and lead this material off through the spout 6.

The bottom of the receptacle 7 is provided with a depending annular flange 11 having a shoulder resting on the frame 3 adjacent an annular recess 12 in the frame. Thus, the flange 11 supports the receptacle on a seat 12a of the-frame in concentric relation to the rotor spindle 2.

It is quite difiicult, of course, to form the radially inwardly directed part of the annular outer wall 9 so accurately that its free inner edge follows closely along the surface of the rotor body 1, whereby the intervening space is small enough to prevent material from the interior of the receptacle from escaping out through this intervening space. According to the invention, this intervening space or slot is made considerably larger than would be suitable to prevent such escape, and the latter is prevented by a substantially plane annular screen 13 placed on the radially inwardly directed part of the wall 9 of the receptacle. The outer periphery of the screen 13 is formed as a circle so that, by lying in contact :ith the surrounding inner annular surface of the frame 3, it is centered by this surface. In addition, the inner edge of thescrcen 13 is provided with an annular downwardly directed flange 14- which overlaps the free inner edge of the wall 9 and extends to the immediate vicinity of the rotor body with which it forms the desired narrow slot. This construction is simpler and cheaper than making the wall 9 in such a way that its free inner edge fits accurately and closely along the rotor body but still does not touch it. At the same time, it has the advantage that the annular slot of the receptacle may be made large enough so that, with the centrifugal bowl 1 and the screen 13 removed, it is easy to insert one hand into the receptacle for cleaning its interior.

The screen 13, on its side turned away from the receptacle (its upper side), is provided with vanes 15 and with tightening springs 16. The vanes 15 are spaced around the screen, and each vane extends at an angle to an intersecting radius of the screen (FIG. 2). A cover 17 with a flange l8 closes the upper part of the frame 3 and is held tightly to it by means of bolts (not shown). The flange 13 of the cover thus presses downward against the leaf springs 16, which are also spaced around the screen and welded to it. Accordingly, through the springs 16, the screen is pressed downward against receptacle 5 so that its bottom flange 11 is held down against the frame 3. In this way, the receptacle 5 is firmly held in position but can be readily detached from the frame.

The frame is provided with a discharge line 19 which is firmly connected to the frame. The spout 6 of the receptacle extends down into the discharge line 19 without being secured to it. The reason for this is that it is desired that, after removing the centrifugal bowl 1, the receptacle be easily detach able from the frame for cleaning the receptacle and also for cleaning the frame internally. A packing 20 is provided between the spout 6 and the discharge line 19.

According to the invention, dirtying of the rotor body 1 as well as the frame 3 is prevented because the slot or space between the screen 13 and the rotor body can be made very small. The dirtying is further prevented because the screen is provided with vanes 15 which darn up air in the slot. The dammed-up air thus forms a barrier to sucking action through the slot between the screen and the rotor body. At the same time, the screen 13 cuts off the chamber 21 from sucking action from the rotor body, which works as a pump, and the packing 20 prevents entry of material from the discharge line 19 into the chamber 21.

I claim:

1. In a centrifugal separator having a frame and a hollow rotor rotatably mounted in the frame, the rotor being provided at its periphery with nozzle outlets for discharging a separated material from the rotor, the combination of an annular receptacle mounted in the frame around the rotor and having an annular inner wall terminating adjacent the rotor at a region located radially inward from the nozzle outlets, the receptacle also having an annular outer wall extending opposite the nozzle outlets and radially inward toward the rotor to form therewith a first annular-slot, said outer wall having a free inner edge partly defining said slot, whereby the receptacle opens toward the nozzles to receive said discharging material, the frame having a seat on which the receptacle is mounted, a substantially'flat annular screen resting on said annular outer wall of the receptacle and having an inner edge portion overlapping said free inner edge of said outer wall and forming with the rotor a second annular slot of substantially smaller width than said first slot, the frame engaging the outer edge of the annular screen to center the same with its inner edge in close surrounding relation to the rotor, a removable cover on the frame urging the screen against the receptacle and thereby holding the receptacle against said seat, the rotor having a partof relatively large diameter overlying the screen and exerting a pump action acting to suck air upwardly from the receptacle through said slots and a series of vanes on the screen at the side thereof facing toward said large diameter part of the rotor and so inclined relative to each other and to the direction of rotation of the rotor as to counteract the suction incident to said pump action.

2. The combination according to claim 1, in which said annular outer wall of the receptacle extends axially of the rotor past the nozzles and then radially inward toward the rotor.

3. The combination according to claim 1, comprising also springs located on the side of the screen remote from the receptacle and through which the cover urges the screen against the receptacle.

4. The combination according to claim 1, in which said inner edge portion of the screen has an annular flange extending downward into the receptacle through said annular slot.

References Cited in the file of this patent UNITED STATES PATENTS 439,173 Newbery et al Oct. 28, 1890 1,845,076 Andersson Feb. 23, 1932 2,047,025 Gilbert July 7, 1936 2,077,813 Strezynski Apr. 20, 1937 2,690,900 Zachariassen Oct. 5, 1954 2,883,054 Sanchez Apr. 21, 1959 FOREIGN PATENTS 79,024 Sweden Nov. 28, 1933 524,473 Italy Apr. 26, 1955 

